SECTION 12
TIRE INFLATION SYSTEM
crankcase and end covers. Also check their oil
valve seats only if they are worn or damaged
passages to make sure they are open and
a n d are being replaced. Unloader bore
clean.
b u s h i n g s should be inspected, but not
removed unless they are damaged.
f. If an oil seal ring is used in the end cover,
12-28. CLEANING, INSPECTION AND REPAIR.
check fit of ring in ring groove. There should
b e 0.008 to 0.015 inch (.203-.361 mm)
12-29. CLEANING.
clearance at the gap when placed in the end
bore of the crankshaft. If the oil ring is worn
a. Clean all parts in solvent before inspection.
thin or is damaged, it should be replaced.
Inspect oil ring groove in end cover; if groove
b. Remove all carbon deposits from dis-
is worn excessively, replace end cover or
charge cavities and all rust and scale from
machine groove for next oversize oil seal ring.
cooling cavities of cylinder head body. Scrape
all foreign matter from body surfaces and use
g. With cylinder block installed on crankcase
air pressure to blow dirt particles from all
check fit of ball bearings in bearing bores.
cavities.
They must be a tight press fit. The crankcase
should be replaced if bores are worn or
c. Discharge valves can be dressed by
damaged.
lapping them on a piece of fine crocus cloth on
h. Check for cracks or broken lugs on
a flat surface, provided they are not excessively
worn.
cylinder block. Also check unloader bore
bushings to be sure they are not worn, rusted
d. Clean carbon and dirt from inlet and
or damaged. If these bushings are to be
replaced, they can be removed by running a
unloader passages. Use air pressure to blow
c a r b o n and dirt deposits from unloader
1/8 inch (3.175 mm) pipe thread tap inside the
bushing. Insert a 1/8 inch (3.175 mm) pipe
passages.
threaded rod and pull the bushing straight up
e. Inlet valves, as in the case of discharge
and out. Do Not use an easy-out for removing
valves, not worn excessively can be cleaned by
these bushings.
lapping them on a piece of fine crocus cloth on
a fiat surface.
i. If inlet valves are grooved or worn where
they contact the seat, they should be replaced.
If the inlet valve seats are worn or damaged so
f. Clean thoroughly all oil passages through
they cannot be reclaimed by facing, they
crankshaft, connecting rods, crankcase, end
should be replaced.
covers and base plate. If necessary, inspect
passages with a wire and blow foreign matter
out with air pressure.
j. Cylinder bores which are scored or out of
round by more that 0.002 inch (.05808 mm) or
tapered more than 0.003 inch (.0762 mm)
12-30. INSPECTION.
should be rebored or honed oversize. Oversize
pistons are available in 0.010, 0.020, and 0.030
a. Inspect cylinder head body for cracks or
inch (.254, 508, .762mm) oversizes.
damage.
k. Cylinder bores must be smooth, straight
b. Use air pressure to test water jackets of
and round.
cylinder head and block for leakage. Replace
unit if leakage Is found.
I. Clearance between cast iron pistons and
cylinder bores should be between 0.002 inch
c. If discharge valves are worn and grooved
minimum and 0.004 inch maximum (.0508 mm
where they contact the seats, they should be
to .1016 mm) (see figure 12-8). Aluminum
replaced. If the discharge valve seats are worn
pistons are cam ground.
excessively so that there Is no longer enough
m. Check pistons for scores, cracks or
metal left to reclaim them by lapping, the seats
enlarged ring grooves; replace pistons if any of
should be replaced.
these conditions are found. Measure each
piston with a micrometer in relation to the
d. Replace all used discharge valve springs
cylinder bore diameter to be sure the clearance
and cap nuts.
is between 0.002 and 0.004 inch (.0508 to .1016
mm).
e . Check for cracks or broken lugs In
12-6.
